The present invention is directed to a voltage controlled oscillator for use in varying the size of objects displayed on a raster type video screen.
Voltage controlled oscillating circuits in which the output signal has a frequency which varies linearly with an analog input voltage are useful in video displays. In particular, such oscillators are useful in electronic circuitry associated with video games. One use of such an oscillator is shown in U.S. patent application Ser. No. 809,314, filed June 23, 1977, in the names of Steven T. Mayer and Ronald E. Milner, and assigned to the assignee of the present invention. In that application, apparatus sold under the trademark "STARSHIP" is provided for changing the size of a displayed object to provide a realistic illusion of perspective.
To provide greater variation in object size it is desirable to use an oscillator having a large frequency range. It is also desirable to provide higher output frequencies which are needed to produce smaller objects. Such a capability allows objects to move to near a vanishing point on an ocean horizon. Heretofore, the only practical method of providing the above increased frequency range needed for such video displays was through heterodyning.